A large number of recent studies have associated a mitochondrial death pathway at reperfusion with both necrosis and apoptosis. Preventing the mitochondrial death pathway, therefore, is a prerequisite for successful cardioprotection at reperfusion. Although adenosine A2 receptor activation at reperfusion has been proposed to protect the heart, its mechanisms are still not clear. The objective of this proposal is to determine the effects of A2 receptor activation on the mitochondrial death pathway and to elucidate the signaling mechanisms underling the effects of A2 receptor activation. We hypothesize that stimulation of A2 receptor activation by NECA at reperfusion interdicts the mitochondrial death pathway through a signal cascade involving eNOS, NO, PKG, zinc, and GSK-3. We will test these hypotheses by using diverse techniques of cell biology, molecular biology, physiology, pharmacology, and gene targeting. Aim 1 will determine the effects of A2 receptor activation at reperfusion on the mitochondrial death pathway by measuring mitochondrial function, infarct size, and indexes of apoptosis. Aim 2 will determine the mechanisms by which A2 receptor activation produces NO by defining the roles of PKA, tyrosine kinase, and HSP90 in activation of eNOS. Aim 3 will determine the role of PKG in the protective action of A2 receptor activation. We will define the role of PKG by overexpressing or knocking out the PKG gene. Aim 4 will ascertain the downstream targets of PKG activation that lead to the preventive effects of A2 receptor activation on the mitochondrial death pathway. Towards this goal we will characterize the roles of intracellular free zinc, mitochondrial KATP channels, and GSK-3. The successful execution of this proposal should produce important new insights into the signaling mechanisms underlying the protective effects of A2 receptor activation at reperfusion against ischemia/reperfusion injury, and have great clinical significance for treating patients with acute myocardial infarction. [unreadable] [unreadable] [unreadable]